Heat treatment of fibers



July l4, 1964 KENlcHl TANABE ETAL 3,140,957

HEAT TREATMENT OF FIBERS Filed Feb. 25, 1961 @Alm INVENTORJS` TANA BE KE/VCH/ H/DEO SAITO United States Patent O 3,140,957 HEAT TREATMENT OF FIBERS Kenichi Tanabe and Hideo Saito, Kurashiki, Japan, as-

signors of three-fourths to Kurashiki Rayon Co., Ltd., Kurashiki-shi, Japan, a corporation of Japan, and of one-fourth to Air Reduction Company, Incorporated, New York, N.Y., a corporation of New York Filed Feb. 23, 1961, Ser. No. 90,929 Claims priority, application Japan Feb. 23, 1960 9 Claims. (Cl. 117-6) This invention relates to the heat treatment of fibers.

In the production of synthetic fibers, it is customary to heat-treat the fibers after they have been formed or spunf The usual methods for the heat treatment of fibers include two general procedures, one involving treatment in gases (including uid powders) and the other involving treatment in liquids. The former method, because of the generally inferior heat conductivity of gases, takes many hours for satisfactory heat treatment, and therefore it is difficult to operate with efciency with this procedure. Thus, the heat-treating oven must be made larger with increase in treating speed and, as a result, it becomes extremely difiicult to maintain the temperature uniform throughout the oven. As the gas, air is commonly employed, and it is a well known fact that fibers generally tend to become discolored by it. On the other hand, in carrying out heat treatment in liquid, aqueous solution of salts or organic liquids, or the like, are generally employed. The boiling point of aqueous solutions of salts is commonly about l-ll0 C. Treatments at temperatures higher than the boiling points of these solutions require the application of pressure, thus complicating the operation.

When using organic liquids, as the heating medium, oils or other organic substances having high boiling points are generally employed. In this case, the heat-treating time is short, and discoloraiton due to the heat treatment is slight. However, because of their generally high vscosity, large quantities of these liquids adhere to the fibers, and accordingly, problems in recovery are presented. Moreover, with the elevation of the treating temperature, the evaporation losses of the liquid heating media increase, and changes in quality due to long hours of continuous use are substantial. More particularly, when the heat-treating bath is operated at high speed, the quantity of heating medium adhering to the fibers amounts to many times the weight of fibers treated, and its reclamation becomes difficult, resulting in an excessively high loss of heating medium. These are some of the factors which make the industrial application of this process difficult.

It is accordingly an object of the present invention to provide a process for the heat treatment of fibers which avoids the drawbacks and disadvantages of prior heattreating processes.

In accordance with the invention, fibers to be heat treated i.e., fibers which are benefited by heat treatment, are first coated with a liquid substance that can be heated to over 50 C. and up to conventional air heat-treating temperatures and which do not have an adverse action on fibers at such heat-treating temperatures, whereupon the coated fibers are subjected to heat treatment in a heated gas, at fixed length, while being elongated, or while being allowed to shrink or relax. In accordance with this process it is possible to effect heat treatment of fibers with ease, efficiency, and uniformity without complex operations, and to minimize discoloration which generally accompanies heat treatment. The accompanying drawing is illustrative of the invention and illustrates in modified flow sheet form the process of the invention and also indicates schematically some of the apparatus 3,140,957 Patented July 14, 1964 useful in carrying out the methods of the present invention. Fiber forming material preparation is not illustrated but identified by the reference numeral 1. Similarly, fiber forming is identified by reference numeral 2. The formed fiber is identified by numeral 3. The path or direction of fiber 3 travel is indicated by small arrows 4-only a representative number of these small arrows 4 carry this reference numeral. A continuously extending fiber 3 is shown from point 5 to point 6. The formed fiber 3 is first passed over a preheat treating roller 7. The preheating step may be eliminated as shown by the dotted travel line 9. Next the fiber 3 passes over and is in contact with roller 10. The roller 10 is freely revolving and rotates because of the fiber 3 movement. Liquid coating material 11 is contained in a suitable tank 12. The lower surface of roller 10 is immersed in the coating liquid 11, resulting in a film of liquid (not shown) on the roller 10. The fiber 3 coming in contact with the liquid film is coated with liquid 11. The coated fiber 16 is shown extending from point 17 to point 18. The coated liber 16 passes to the heat treatment chamber 25. Heating is provided by introduction of heated air 20 or inert gas 20. After the heat treatment is completed the fiber 16 passes to the washing apparatus 30. Illustrated is a tank 31 containing water 32. The fiber 16 is passed through the water 32 to remove the liquid 11 that was applied in the previous coating step. The washed fiber 35 is now illustrated by the line 35 extending from point 13 to point 6. The washed fiber 35 then passes to and then through the drying chamber 36. Heated air 20 or inert gas 20 is introduced into the chamber 36. Finished fiber product 42 is shown leaving the drying chamber 36 and passing to point 6. A representative number of the other rollers are identified by the reference numeral 50.

We have found out that in carrying out the heat treatment of fibers in accordance with our invention, operation can be effected not only with ease and at high speed while making it possible to shorten the heat treating time in comparison with conventional heat treatment in gases, and to lessen discoloration of the fibers, but also to curtail the loss of heating medium as compared to experience in the heat treatment of fibers in liquids.

In applying the method of the invention, the effect will be all the more substantial if the fibers are preheated to SiO-200 C. The materials to be adhered to or coated upon fibers are those which do not damage fibers at the temperatures of heat treatment, and are in a liquid state at such temperatures, although they may be used in solution, and furthermore, are as stable as possible at the heat treating temperature, and at the same time, can be easily washed from the fibers. Illustrative examples of liquids filling these conditions, and suitable for use in carrying out the process of this invention, include hydrocarbons or their derivatives, e.g., halogen derivatives, such as liquid paraffin, solid parafiins, parafiin halides, mineral-oils, alkyl-benzenes, diphenyl, diphenyl-chloride, diphenyl-ether, and diphenyl-amine, and the like, polyhydric-alcohols such as medium and high molecular weight alcohols, alkylene glycol, glycerine, and the like, polyethers such as polyalkylene-glycol, amines such as polyethanol-amine, medium or long-chain aliphatic acids, or their esters, silicone oils, and the like. More particularly, as shown in Examples l to 7 below, the fibers are coated with materials which can be characterized as hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils. q

The invention will be further understood from the following experimental data:

Polyvinyl alcohol fibers tow (600 filament, 400.0 denier), spun by the conventional melt spinning process and dried, were continuously heat-treated under various conditions as shown in Table l, and their properties were measured. Preheating was effected on a heating roller. The polyethylene glycol was heated in a beaker. The lower surface of a freely revolving small roller was irnmersed in the liquid to be coated on the fibers, i.e., the

ment. The heat treatment is carried out in air, and therefore, lesser resistance is encountered during the treatment as compared to the treatment in liquid, and the method of this invention is particularly advantageous for heat polyethylene glycol, and the upper surface of the roller, 5 treatment with drawing, shrinking, and the like. which was not immersed in the liquid body but which This process thus has important industrial advantages carried a film of the polyethylene glycol, was kept in conand, as mentioned, it is applicable to heat treatment with tact with the tow to be treated. The roller was rotated drawing, shrinking, or at fixed length. Similarly, the by the movement of the fibers, and the liquid was transprocess is applicable not only to polyvinyl alcohol fibers, ferred from the surface of the roller and applied to the but also to various natural fibers, regenerated fibers, and fibers at the rate of about 1/2 part by weight per part by especially to thermoplastic synthetic fibers, as will be weight of fiber. The air heat-treating machine used was demonstrated in the examples. of conventional type. The invention will thus be further understood from TABLE 1 Preheat- Temper- Temper- Heat Maxiing ature of ature of Treatmum Dry Test temperpoly- Heat ment elonga- Strength Dis- No. ature ethylene Treat- Tirne tion (g./d./ coloration C.) glycol meut (Sec.) (percent) None used. 230 l0 200 7. 9 Negligible. do 230 a0 265 s. 7 slight yellow.

230 60 280 9. l Yellow. 230 l0 210 8. 2 Negligible. 23o 1o 26o 8.9 Do. 23o 30 3io 1o. 1 slight yellow. 230 10 285 9. 5 Negligible. 23o 5 265 9.0 Do.

From the results tabulated above, it is seen that in the following specific examples of practical application. the case of the drawing of fibers heat treated in air with- However, it will be understood that these examples are out the application of polyethylene glycol, insufiicient not to be construed as limiting the scope of the present elongation in 10 seconds of elongation was observed. A invention in any manner. In the examples, all parts are by considerable increase in the elongation is seen in sec- 35 weight unless otherwise indicated. onds, and one minute drawing brings about maximum Ex l 1 elongation, but further prolongation of time does not amp e contribute to any increase in elongation, but only serves IolyVinyl aleohol iiherS (3000 denier, 600 filaments) to deepen the coloration. However, when these fibers produced bv Conventional Wet Spinning were preheated were heat-drawn in an air bath after polyethylene glycol on a roller at a temperature 0f 130 C., and Polyethylene heated to 240 C. was applied to them, `10 seconds of drawglycol heated to 240 C- WaS 'dPPlied as a Coating t0 the ing gave an elongation substantially equivalent to the value liber S- The iiher S Were then drawn 3-9 tintes their length which 30 seconds of drawing did in the case of no apin 8 SeCOndS at 230 C in an ail' bath While held at plication of polyethylene glycol, and thus the time of fixed length the fibers were heat treated in an air bath drawing was shortened to about 1/3. Discoloration due to for s Seconds at 235 Co and Were then Continuously heat was slight. washed with water and dried. There were thus produced Furthermore, when the libel-S were subjected to the beautiful white fibers exhibiting good hot water resistance same treatment after preheating, the effect of the invenand not dissolving in boiling water even immediately tion became all the more apparent, the time required for after the heat treatment, and having a dry Strength 0f drawing was shortened to around 1&5, and moreover, 9.8 g./denier. However, when the fibers were hot drawn fibers of minimum discoloration were obtainable. when in an air bath, and Subsequently. at fixed length, Were the heated polyethylene glycol was not applied to the subjected to heat treatment without the application of fibers, the effect of preheating was found to be negligible. Polyethylene glycol, they diSSolVed readily in boiling Water The new results obtainable by this invention are clear eVen after only 30 SeCondS 0f drawing at 230 C-i Where' from the date in Table 1. on the other hand, when in they were drawn 38 times in length, and even after fibers are heat treated in a C g, polyethylene glyo]y SeCOndS Of heat treatment at flXed length at 235 some time shortening is, of course, obtainable. However, The herS Were light yellow in Color, and had 21 dry as the treating speed increases, the amount of liquid which Strength of 9.4 g./ denier. clings to the fibers becomes excessive, and after a prolonged period of use, the liquid degenerates seriously. Example 2 With the resultant increase in viscosity, the quantity of Polyvinyl alcohol fibers spun by conventional dry liquid adhering to the fibers increases further, amountspinning method were preheated on a roller at 20 C., ing to several times the weight of the fibers. Then, not and silicone oil heated to 235 C. was applied as a coating only does the reclamation of the liquid from the fibers to the fibers. The fibers were then stretched 9 times in become difficult, but the rate of degeneration of the liquid length in 1.5 seconds at 230 C. in a nitrogen (inert gas) increases and its recovery becomes still more difiicult. atmosphere and were subjected to a 10% shrinkage heat These serious disadvantages and drawbacks are greatly treatment in nitrogen at 233 C. for 1.5 seconds. They reduced by the method of this invention. were then continuously washed and dried. The product The quantity of liquid applied to the fibers in the was in the form of beautiful white fibers capable of withprocess of this invention can vary from about 10% of standing boiling water even immediately after heat treatthe weight of the fibers upwardly and amounts up to ment, and exhibiting a dry strength of 7.9 g./denier, and about 50% of the weight of the fibers are preferred. By an elongation of 12%. However, when another batch of such coating, treating-time shortening and the uniformity the same original fibers were stretched with heat and of treatment similar to those obtained by conventional subjected to shrinkage heat treatment in a nitrogen atmosheat treatment in liquid are realized without the abovephere without the application of silicone oil, after stretchmentioned disadvantages of conventional liquid heat treating at 230 C. for only 5 seconds, its length was increased 8.8 times, and the fibers subjected to a shrinkage heat treatment for 5 seconds dissolved in boiling water. They had a dry strength of 7.7 g./ denier, and an elongation of 11.5%.

Example 3 Fibers spun by injecting a spinning solution, prepared by adding boric acid (in the proportion of 1.2% based on the polyvinyl alcohol) to a aqueous solution of polyvinyl alcohol, into a saturated aqueous Glaubers salt solution at 30 C. to which 3 g./ liter of caustic soda had been added. The product fibers were thoroughly washed with Water to free them of boric acid and Glaubers salt, and they were preheated with infra-red rays. Polyalkylene glycol heated to 235 C. was then coated on the fibers, and they were stretched 3.5 times in length at 230 C. in 10 seconds in a nitrogen atmosphere. At fixed length the fibers were subjected to heat treatment in an air bath at 235 C. for 'l0 seconds, followed by continuous washing and drying. In this way, beautiful white fibers capable of withstanding hot water of 120 C. and having a dry strength of 14.2 g./denier even immediately after heat treatment were obtained.

However, when the original fibers were stretched with heat in an air bath, and at fixed length were subjected to heat treatment, but with no application of an organic liquid, they elongated only by 1.8 times at 230 C. for 30 seconds, and the fibers subjected to heat treatment at 235 C. for 30 seconds at fixed length withstood only up to 102 C. in hot water. The dry strength was 8.3 g./ denier, and the fibers were light yellow in color.

Example 4 After glycerine heated to 130 C. was applied as a coating to polyethylene fibers melt-spun in conventional manner by means of an extruder, the fibers were stretched six times in length at 130 C. in 6 seconds in steam, followed by continuous washing with water and drying. There were obtained beautiful fibers having a dry strength of 7.5 g./ denier, and an elasticity of 19%. However, when the same fibers were stretched in steam without the application of glycerine, their length was increased only 6 times at 130 C. and after 20 seconds. The dry strength was 7.2 g./ denier, and the elasticity 18%.

Example 5 Oleic acid heated to 200 C. was applied as a coating to nylon fibers produced by conventional melt-spinning, and the fibers were stretched 4 times in length in one second at 200 C. in air. While at fixed length, the fibers were subjected to heat setting in an air bath at 205 C. for a second, followed by continuous washing and drying. In this Way there were produced beautiful fibers having a dry strength of 6.3 g./denier and an elasticity of 34%. When, however, the original fibers were stretched with heat and subjected to heat treatment in an air bath without the coating of oleic acid, 3 seconds stretch at 200 C. effected 3.9 times elongation, and the subsequent heat treatment at fixed length at 205 C. for 3 seconds gave a dry strength of 5.9 g./denier, and an elasticity of 33 Example 6 Acetate fibers spun by the conventional dry spinning process and stretched were subjected at fixed length to heat setting for 2 minutes in an air bath at 180 C. The heat setting was effective in making the fibers resistant to warm water at 70 C.

However, when fluid parafiin heated to 180 C. was coated upon the fibers, which were not preheated, and the fibers were then subjected to heat setting at 180 C. for 30 seconds in an air bath, followed by continuous Washing and drying, the heat setting enabled the fibers to withstand warm water of 80 C.

6 Example 7 The elasticity of viscose rayon spun by the conventional wet spinning process was about 3740% at an elongation of 5%. The fibers were subjected to curing and Soaping for 3 minutes at 140 C., after the fibers were soaked in a 5% aqueous solution of dimcthylol ethylene urea, followed by dehydration and drying. The elasticity at 5% elongation was improved to 50-55%. In a companion test, in processing the fibers after the resin treatment, the curing and then the Soaping were effected at '140 C. for 40 seconds in an air bath after ethylene glycol heated to C. was coated on the fibers. In this case the elasticity was found to be S13-58%.

The conditions and the relative relationships set forth in the examples are those preferred in carrying out the process of this invention, but it will be understood that other conditions and relationships may be used within the scope of the invention. In general, unless otherwise indicated, conventional operations and techniques are suitably employed.

Thus, heat treatment is usually carried out by heating the fibers in a gaseous medium, such as air, at a temperature ofl 210-250 C. for 2 seconds to 5 minutes, and in accordance with this invention the time of treatment is preferably 2 seconds to 1 minute.

As previously mentioned, the fibers may be heat treated at fixed length or they may be stretched or relaxed in accordance with conventional techniques as illustrated, for example, in U.S. Patent 2,636,803, 2,636,804 and 2,906,594.

Similarly, other conventional treatments may be applied to the fibers such as acetalization, also in accordance with conventional techniques, but such treatment form no part of the present invention.

It will also be understood that various changes and modifications in addition to those indicated above may be made in the embodiments herein described without departing from the scope of the invention as defined in the appended claims. It is intended, therefore, that all matter contained in the foregoing description shall be interpreted as illustrative only and not as limitative of the invention.

We claim:

1. A process for the heat treatment of organic fibers benefited by heat treatment which comprises the steps of coating the fibers with a liquid substance resistant to temperatures up to about 250 C., said liquid substance being selected from the group consisting of hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils and then exposing said fibers to a member of the group consisting of air and an inert gas heated to a temperature of at least about 140 C.

2. A process for the heat treatment of organic fibers benefited by heat treatment which comprises the steps of coating the fibers with a liquid organic high molecular weight substance resistant to temperatures up to about 250 C., said liquid substance being selected from the group consisting of hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils and then exposing said fibers to a member of the group consisting of air and an inert gas heated to a temperature of at least about 140 C.

3. A process for the heat treatment of organic fibers benefited by heat treatment which comprises the steps of preheating the fibers to a temperature of 50 to 200 C., coating the fibers with a liquid substance resistant to temperatures up to about 250 C., said liquid substance being selected from the group consisting of hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils and then exposing said fibers to a member of the group consisting of air and an inert gas heated to a temperature of at least about 140 C.

4. A process for the heat treatment of organic fibers benefited by heat treatment which comprises the steps of preheating the fibers to a temperature of 50 to 200 C coating the fibers with a liquid substance resistant to temperatures up to about 250 C., said liquid substance being selected from the group consisting of hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils and then exposing said fibers to a member of the group consisting of air and an inert gas heated to a temperature of at least about 140 C. up to about 250 C. for a period of time up to about 1 minute.

5. In the process for the heat treatment of organic fibers benefited by heat treatment with a member of the group consisting of air and an inert gas heated to a temperature of at least about 140 C., the improvement which comprises coating the fibers with a liquid substance resistant to temperatures up to about 250 C. prior to exposing said fibers to the heated gas, said liquid substance being selected from the group consisting of hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils.

6. In the process for the heat treatment of organic fibers benefited by heat treatment with. a member of the group consisting of air and an inert gas heated to a temperature of at least about 140 C., the improvement which comprises preheating the fibers to a temperature of 50 to 200 C. and coating the fibers with a liquid substance resistant to temperatures up to about 250 C. prior to exposing said fibers to said heated gas, said liquid substance being selected from the group consisting of hydrocarbons, polyhydric alcohols, amines, polyethers, long-chain aliphatic acids, and silicone oils.

7. A process for the heat treatment of organic fibers as defined in claim 1, wherein said fibers are selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, nylon fibers, acetate fibers, and viscose rayon fibers.

8. A process for the heat treatment of organic fibers as defined in claim 3, wherein said fibers are selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, nylon fibers, acetate fibers, and viscose rayon fibers.

9. A process for the heat treatment of organic fibers as defined in claim 6, wherein said fibers are selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, nylon fibers, acetate fibers, and viscose rayon fibers.

References Cited in the file of this patent UNITED STATES PATENTS 1,959,350 Ellis May 22, 1934 2,176,153 Semon Oct. 17, 1939 2,346,208 Conaway Apr. 11, 1944 2,418,927 Freund Apr. 15, 1947 2,461,841 Nordberg Feb. :15, 1949 2,938,811 Hermes May 31, 1960 2,990,604 MacCormack July 4, 1961 3,012,905 Tillisch Dec. 12, 1961 3,024,081 Frost Mar. 6, 1962 3,050,820 Pamm Aug. 28, 1962 

1. A PROCESS FOR THE HEAT TREATMENT OF ORGANIC FIBERS BENEFITED BY HEAT TREATMENT WHICH COMPRISES THE STEPS OF COATING THE FIBERS WITH A LIQUID SUBSTANCE RESISTANT TO TEMPERATURES UP TO ABOUT 250*C., SAID LIQUID SUBSTANCE BEING SELECTED FROM THE GROUP CONSISTING OF HYDROCARBONS, POLYHYDRIC ALCOHOLS, AMINES, POLYETHERS, LONG-CHAIN ALIPHATIC ACIDS, AND SILICONE OILS AND THEN EXPOSING SAID FIBERS TO A MEMBER OF THE GROUP CONSISTING OF AIR AND AN INERT GAS HEATED TO A TEMPERATURE OF AT LEAST ABOUT 140*C. 